5 Answers
5

I've had an iPhone 4 since the day it came out. After the first year or so the oleophobic property has completely gone: it's now no different to my old iPhone 3G screen in terms of finger smears. I've never cleaned it with any sort of chemical agent but I've also never kept it in a case that covers the screen, and it spends a lot of time in my jeans pocket. So the answer is yes, under some conditions it certainly does wear off over time. Your mileage may vary, of course: kept in a case, or carried in a bag or purse where the screen doesn't get rubbed, it should last much longer.

As they say, your mileage may vary. I would say that it all depends on the cleaning solution you use.

I had an iPhone 3G that I used for quite some time and cleaned regularly with the cleaning kit by iClear (The only one that Apple sells at its stores). I cleaned the iPhone about once a week and it kept the screen in excellent condition.

For my iPhone 4, I have been using the cleaning kit by Monster sold at Best Buy (also weekly) and it has not kept my phone as well as the cleaning kit by iClear. This tells me that the oleophobic coating may actually diminish over time with the wrong cleaning solution.

Unfortunately, yes, the coating does wear off over time. Apple has this to say:

Please note that the ability of this coating to repel oil will
diminish over time with normal usage, and that rubbing the screen with
an abrasive material will further diminish its effect and may scratch
your screen. —Apple

However, and this is good news, there are aftermarket alternatives to re-apply an oleophobic coating. Aculon is in the business of applying lipophobic protection (among other types) to a range of devices. I'm not sure how well they work or how much they run but a solution does indeed exist.

And for the curious bunch among you, here's what Bill Nye (The Science Guy) says on how the substance works:

The new 3GS iPhone has a coating that helps you leave no, well hardly
any, prints—fingerprints. The glass screen is coated with a polymer,
a plastic that human skin oil doesn't adhere to very well. People in
the chemical bonding business like to call the finished surface
"oleophobic."

Such a lovely Greek cognate may sound like it means "afraid of oil."
And, it does, but it also connotes (or carries with) "aversion" or
"not-like-to-be-around-tivity," if I may. Instead of sticking to the
bonded-plastic surface of your new phone, the oil from you fingers or
cheekbone or tip of your nose stays more or less together as its own
smooshed droplet.

The Applers were able to do this by bonding this oleophobic polymer to
glass. The polymer is an organic (from organisms) compound,
carbon-based. The glass is nominally inorganic, silicon-based… solid
rock. The trick is getting the one to stick to the other. Although it
is nominally proprietary, this is probably done with a third molecule
that sticks to silicon on one side and to carbon-based polymers on the
other side. Chemical engineers get it to stay stuck by inducing
compounds to diffuse or "inter-penetrate" into the polymer. The
intermediate chemical is a "silane," a molecule that has silicon and
alkanes (chains of carbon atoms).

If you'd like—and I hope you will—take a moment and think about
droplets, like water droplets, on a surface. Deep in the droplet,
water molecules stick to each other. On the surface though, they stick
to each other as well, but they also have to opportunity to stick or
not to stick to the surface they're resting on. When they stick, say
to the nylon fibers in a bikini strap, the swimsuit feels wet (or so
I'm told). When they don't stick to the surface they're resting on,
they bead up, like in the car wax commercials.

Well, the polymer that the 3GS iPhone screen is coated with doesn't
let the oil of your skin stick to it very much. So, you don't leave
fingerprints. The key is in the intermediate compounds, the silanes
that hold the plastic to the glass.

So grab a hold of one, and for a change, watch almost nothing happen.
It's chemistry. —Gizmodo